ABC26GN4573 · Area

Subject: General Aptitude · Chapter: Area · Exam: 2007 · Marks: · Difficulty:

If the wheel of the engine of a train $4 \frac{2}{7}$ metres in circumference makes 7 revolutions in 4 seconds, then the speed (in km/hr) of the train is

(a)27

(b)28

(c)29

(d)30

Answer

Answer (as printed): A

Explanation

Distance covered in $4 \sec =\left(\frac{30}{7} \times 7\right) \mathrm{m}=30 \mathrm{m}$. Distance covered in $1 \sec =\frac{30}{4}$ Distance covered in 1 revolution $=\left(\frac{30}{4}\right) \mathrm{m}=\frac{15}{2} \mathrm{m}$. ∴ Required speed $=\left(\frac{15}{2}\right) \mathrm{m} / \mathrm{s}=\left(\frac{15}{2} \times \frac{18}{5}\right) \mathrm{km} / \mathrm{hr}=27 \mathrm{km} / \mathrm{hr}$.

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